Over the past decade, significant increase in the concentration levels of arsenic and fluoride in surface water have been reported throughout the world. The primary reason is the rapid decline in the water table as increasingly more surface water is exploited for irrigated agriculture, and rural and urban water supply. Risk to the human health has increased with increased concentration levels of these solutes in potable water. Adsorption has shown considerable potential in removing arsenic and fluoride from water. While many technologies such as precipitation and coagulation, chemical oxidation, membrane, ion-exchange, and biological treatment are also in place for the removal of contaminants, such as arsenic and fluoride, from wastewater exist they are not efficient, cost-effective, and applicable to where water is scarce.
A variety of adsorbents have been previously developed for the removal of fluoride and arsenic from wastewater. Activated alumina and alumina supported metal oxides are common adsorbents used for defluoridation applications. Activated carbon or metals impregnated with activated carbon has also achieved limited success. Activated carbon micro- and nanofibers dispersed with Al was synthesized, and found effective in removing fluoride from wastewater. With regard to the remediation of arsenic laden wastewater, there have been studies on the development of Fe-modified activated carbon in the form of either powders or granules or fibers. With Fe possessing large and selective affinity towards arsenic because of the formation of strong surface complexes, and activated carbon providing a large surface area for impregnation, a variety of Fe-doped carbon based adsorbents have been synthesized for the removal of arsenic. Fe-doped activated micro/nano carbon particles have also been developed as adsorbents for arsenic removal.
Previous adsorbents were either made with inferior processes or do not adsorb a sufficient quantity of contaminants. There is still a need for improved adsorbent materials.